The invention starts with a wiper arm with a wiper blade that is connected in an articulated manner according to the pre-characterizing clause of claim 1.
Known windshield wipers have a wiper arm constructed of a fastening part and an articulated part, which is connected to the fastening part in an articulated manner and has a wiper rod. Connected to the wiper arm in an articulated manner is a wiper blade constructed of a supporting bracket system with a center bracket and possibly subordinate brackets; for example, an intermediate bracket and/or claw brackets to hold a wiper strip. The brackets are also connected with the subordinate brackets in an articulated manner so that during the rotating movement the wiper strip can adapt to a curvature in the vehicle window. Such windshield wipers are known from DE 37 44 237 A1. The joints between the brackets are normally formed by plastic parts, which simultaneously cover the front side of the profile of the higher-order bracket.
In addition, a supporting element made of an elastic, high-strength plastic for a wiper strip is known from DE 197 38 232 A1, whose supporting element has a curvature in an unloaded state that is designed so that uniform application force is produced when the wiper strip is applied completely to the vehicle window during operation of the wiper blade. Caps made of plastic are mounted on the front sides as a termination to the profile. Similar wiper blades with a supporting element made of spring steel are also known. Both a supporting bracket system as well as a supporting element in the sense described above shall be understood in the following as a wiper strip support.
Wiper blades frequently tend to vibrate during the wiping process. Especially with relatively long wiper blades, the guidance on the joint between the wiper blade the wiper arm is not sufficiently stable to prevent these vibrations. The wiper blade is incited to vibrate since a wiper blade is a slim component and because of great speed differences between the drive-side inner area and the outside area of the wiper blade that produce different friction conditions, as well as due to the stick-slip effects. This leads, particularly on the inner circle of the wiper blade where especially low friction speeds are predominant, to undesired lateral movements, which starting at a certain size can lead to the wiper blade impacting the wiper arm and causing a clattering noise. This is particularly critical if the vehicle windows are dry, dirty, iced-up not moist enough or if there is snow on the vehicle window. Since the wiper blade can then lose contact with the vehicle window in the short-term, the wiped image is also unsatisfactory. The more bracket parts the wiper blade has, the sooner it tends to rattle. In addition, light wiper blades with low spring rigidity behave less favorably than others.
In addition, a device to guide the wiper blade is known from DE 197 31 683 A1, which has a first and a second part. It is arranged in the area of the coupling location of the claw bracket and permanently connected with the articulated part of the wiper arm via, for example, adhesion, welding, soldering clipping, clamping, etc.,. The first part of the device has guide cheeks which, with respect to the wiper arm, grip around the articulated location of the claw bracket and guide. The second part also has guide cheeks, between which the first part is guided in a telescoping manner so that its guide cheeks can be held briefly and a collision with the vehicle window is not to be feared even when the vehicle window has a strong curvature. The first part is appropriately connected with the device so that it is secure from loss, for example, via a flexible element.
The second part can also be composed of a spring tongue, which connects the first part to the device so that the first part is rigidly guided in the movement direction of the windshield wiper while it can give way vis-à-vis the wiper arm, perpendicular to the vehicle window. Naturally, it is also possible to select a combination of a spring tongue and guide cheeks as a second part, whereby the spring tongue can assume the function of the flexible element. In addition, the device can be manufactured and composed of individual sheet metal parts, but it is preferable that it be composed of a plastic injection molded part made of a suitable plastic. In any case, additional components are required to guide the wiper blade, whereby increased expenditures for fabrication and assembly, and additional material costs are incurred. An air gap is normally provided between the guide surfaces of the device in order to prevent the joint between the wiper blade and the wiper arm from jamming due to wiper-arm geometry that is influenced by tolerances such as right angles on the wiper rod. Clattering noise can also occur in this case, because, though the lateral vibrations are strongly diminished, they are not avoided completely.
According to the invention, a second end of the connecting blade is fixed on the wiper blade and the connecting blade features an area that is flexible in the longitudinal direction. Fixing the connecting blade on both ends, namely first to the wiper arm, and secondly to the wiper blade, results in guidance between the wiper arm and wiper blade that is free of play, which is especially suitable for flat windshield wipers. In this connection, the wiper arm can run above the wiper blade or laterally offset from it.
The area of the connecting blade that is flexible in the longitudinal direction makes it possible that, with relative movements between the wiper arm and the wiper blade, the connecting blade can give way in the longitudinal direction and thereby create a required longitudinal compensation for the relative stroke between the wiper arm and the wiper blade. As a rule, the connecting blade is designed to be very soft in movement in a direction perpendicular to the windshield, so that the bearing forces of the wiper blade do not change noticeably. The connecting blade is embodied sufficiently rigidly parallel to the windshield, thereby yielding a good lateral guidance of the wiper blade.
In order to be able to assemble and disassemble the wiper blade simply, it is advisable that the connecting blade be fixed detachably to the wiper arm or the wiper blade at least on one end. The other end can be permanently connected to the respective component. Thus, for example, the connecting blade can be welded, soldered or adhered into one end in a U-shaped profile of the articulated part of the wiper arm, while the other end is connected to the wiper blade, particularly the wiper strip support, via two coupling parts that engage with one another. It is advantageous here for the connecting blade to feature an initial stress in the longitudinal direction in an assembled state.
The connecting blade can also be permanently connected to the wiper blade by its being formed on a plastic cap of the wiper strip support or being cast with one end in the cap via injection molding. Other permanent connections with the cap or a part of the wiper strip support are also possible. In this case, a coupling element is provided on the other end of the connecting blade, which is fixed with an adequate press fit in the U-shaped cross-sectional profile of the articulated part or cooperates with another coupling that is fastened to the wiper arm. The coupling parts on the wiper-arm side or on the wiper-blade side can be designed so that they form a ball-and-socket joint. This can compensate for angular deviations without force. The ends of the connecting blade can also be fixed by means of a clip piece on the wiper arm or the wiper blade, whereby the clip piece engages in recesses or indentations of the component with locking elements, for example in the form of noses or corresponding projections.
The connecting blade itself must have suitable elasticity. It can be fabricated of a suitable plastic, preferably one of fiber-reinforced plastic, or appropriately springy steel. The area that is flexible in the longitudinal direction, is formed in a preferable manner by an undulated area of the connecting blade, whereby the width of the connecting blade in the undulated area runs approximately parallel and/or perpendicular to the windshield. In all cases, longitudinal compensation takes place in the longitudinal direction with a relative movement between the wiper arm and the wiper blade. If the width of the connecting blade is aligned parallel to the windshield, greater flexibility is achieved in the perpendicular direction, while flexibility parallel to the windshield can be achieved with alignment perpendicular to the windshield to compensate for manufacturing tolerances. Both possibilities can be combined if the connecting blade is correspondingly limited around its longitudinal axis.